Combustion equipment of gas-turbine engines



Se t. 12, 1961 F. R. MURRAY 2,999,359

COMBUSTION EQUIPMENT OF GAS-TURBINE ENGINES Filed April 24, 1957 2 Sheets-Sheet l [1491. W W I Sept. 12, 1961 F. R. MURRAY COMBUSTION EQUIPMENT OF GAS-TURBINE ENGINES Filed April 24, 1957 2 Sheets-Sheet 2 rates 2,999,359 COMBUSTION EQUIPMENT OF GAS-TURBINE ENGINES This invention comprises improvements in or relating to combustion equipment of gas-turbine engines, and the invention is applicable to combustion equipment of the kind comprising a series of flame tubes, each in an individual tubular air casing, to combustion equipment of the kind comprising a series of flame tubes disposed within an annular space between coaxial annular air casing walls, and to combustion equipment of the kind comprising an annular flame tube coaxially within an annualr space between coaxial annular air casing walls.

This invention has for an object to secure improved combustion of fuel in such combustion equipment.

According to the present invention, in combustion equipment of a gas-turbine engine of the kind comprising a flame tube or flame tubes and an air casing or air casings, there is provided first means to introduce fuel and air into a first region of the flame tube adjacent its upstream end (considered in the general direction of flow through the combustion equipment) in a manner to produce a swirling motion in one direction, the fuel and air being substantially in their stoichiometric ratio, and second means to introduce fuel and air into a second region of the flame tube just downstream of the first region in a manner to produce a swirling motion in the opposite direction. It is found that by adoption of the invention improved combustion is achieved.

Preferably the first means is located at the local centre line of the flame tube and is adapted to cause the fuel/ air mixture in the first region to flow from the point of introduction towards the walls of the flame tube, then upstream, then inwards towards the local centre line and then in the downstream direction, and the second means is arranged to cause at least the air introduced into the second region first to flow towards the centre line, then upstream, then towards the walls and then downstream.

Four embodiments of combustion equipment in which the fuel and air are delivered in accordance with this invention, will now be described with reference to the accompanying drawings, in which FIGURE 1 shows in axial section a first embodiment,

FIGURE 2 is a similar view of a second embodiment,

FIGURE 3 is a similar view of a third embodiment,

FIGURE 4 is a similar view of a fourth embodiment, and

FIGURE 5 is a section on the line 5-5 of FIGURE 4.

Referring first to FIGURE 1, there is shown combustion equipment comprising a flame tube arranged within a tubular air casing 11 so that there is an air passage around the flame tube.

The air casing 11 comprises a diifuser section 11a which is connected to compressor means (not shown) of the gas-turbine engine, and a main section 11b which extends from the diffuser section to the nozzle structure of the associated turbine (not shown).

The flame tube 10 comprises an upstream section 12 having an inlet 13 facing the entry of the difiuser section 11a of the air casing, and a downstream section 14 having in its walls large apertures 15 for the flow of air from the space between the flame tube 10 and air casing 11 into the interior of the flame tube.

The upstream section 12 of the flame tube 10 has mounted within it a tubular member 16 with a domed 23%,359 Patented Sept. 12, 1961 end and this member defines the upstream end of the combustion space. The wall of the member 16 is generally parallel to the wall of the upstream section and is held in spaced relation thereto by a flange 17. Part of the air entering the flame tube through inlet 13 flows in the direction of arrow 18 between the walls of the upstream section 12 and the tubular member 16 to flow into the combustion space in the main through a ring of holes 20 formed in the tubular member 16 just upstream of the flange 17. A minor flow also occurs through apertures in the flange 17.

Mounted coaxially Within the tubular member 16 and projecting into the combustion space are first means for introducing fuel and air into the combustion space. This means comprises a tube 21 which opens through the domed end of the tubular member to have an entry facing the inlet 13, which has a waisted portion so that the tube is of venturi form and which has secured to its downstream end a cap 22 having a frusto-conical side wall formed with a ring of holes 23. This means also comprises a spider having a hollow boss 24 coaxially within the tube 21 and a series of, say four, radiating tubular arms 25 which extend from the boss through the wall of the tube 21 upstream of its waist. The bore of the boss 24 has an entry facing the inlet 13 and the arms 25 aiford air passages leading from the bore of the boss to externally of the tube 21. This means also comprises a fuel injector 26 supplied with liquid fuel by a conduit 27 and spraying fuel into the hollow boss 24. A frusto-conical baffle 29 is secured to the inner surface of the tubular member 16 to project towards the waist of the tube 21.

There is also provided second fuel and air injection means which is afforded in part by the holes 20 and in part by a fuel injector 28 projecting into the flame tube 10 and having an outlet orifice 30 injecting fuel in the upstream direction.

The injector 28 also has a downstream facing fuel orifice 31.

In operation, part of the air entering the diffuser section 11a flows through the inlet 13 and the remainder flows outside the flame tube 10 towards the apertures 15.

The air flowing through the inlet 13 flows (a) in part into the hollow boss 24, where fuel is sprayed into it, and the resulting air/ fuel mixture then flows out through the arms 25 to be deflected by the baffle 29 along the outside of the tube 21, (b) in part through the tube 21 to the ring of holes 23- to be directed outwardly towards the wall of the tubular member 16, and (c) in part as shown by the arrow 18 towards the holes 20 and the strip.

The air/fuel mixture from the arms 25 and the air from the holes 23 combine in the combustion region 32 in a manner to produce a swirling motion as indicated by arrows 33, in which the mixture flows towards the wall of the tubular member 16, then in the upstream direction, then towards the tube 21 and then in the downstream direction. It is arranged that the fuel and air burning in the combustion region 32 are in their stoichiometric ratio.

The air entering the combustion space through the holes 20 and the fuel injected into the combustion space through the fuel orifice 3t combine in a combustion region 34 which is just downstream of the combustion region 32, in a manner to produce swirling motion which is in the opposite sense to the swirling motion in the region 3 2 and which is indicated by the arrows 35. Thus in the region 34 the motion of the burning air/fuel mixture is towards the centre line of the flame tube, then in the upstream direction, then towards the walls of the tubular member 16 and finally in the downstream direction.

The combustion products from the regions 32 and 34 flow downstream where further fuel is mixed them from the orifice 31 to burn with excess air in the products and with air entering the combustion space through the apertures 15, which latter air additionally cools the combustion products.

It is found that by arranging the combustion to take place in adjacent regions in which swirling motions are produced in opposite senses, the combustion efliciency of the combustion equipment is improved.

Referring now to FIGURE -2, there is illustrated combustion equipment of the fuller annular kind comprising inner and outer air casing walls 40 and 41 respectively and in the space between the air casing walls inner and outer annular flame tube walls 42 and 43 respectively. The walls 42, 43 are made in a number of sections and have adjacent their downstream ends large apertures 44 through which air flowing in the spaces between the inner walls 40*, 42 and outer walls 41, 43 can enter the combustion space afforded between the flame tube walls 42 and 43.

The upstream edges of the flame tube walls 42, 43 are spaced apart to provide an air entry 45 to between these walls. Secured tothe inner surface of the outer flame tube wall 43 and to the outer surface of the inner flame tube wall 42 there are annular air-flow dividing members 46, 4-7 respectively.

Each of the members 46, 47 is generally shaped to conform to the adjacent portions of the adjacent flame tube walls 43, 42 respectively and each is provided at its downstream end with a flange 48 by which it is attached to the associated flame tube wall and at its upstream end With an inturned flange 49 extending parallel to the axis of the combustion equipment, these flanges 49 being spaced apart to form an air entry to between the annular members 46, 47. The annular members have formed in them just upstream of the flanges 43 a ring of holes 50 by which air flowing between the annular members 46, 47 and the adjacent flame tube walls 43, '42 can enter the combustion space of the flame tube.

Extending radially between'the annular members 46, 47 and secured to the downstream ends of the inturned flanges 49, there is an annular member of such section as to have a circumferential ridge 51 projecting downstream, which ridge closes the end of the passage between the flanges 49, and radially on each side of the ridge circumferential downstream facing troughs 52. The sides of the ridge are formed with rings of holes 51a.

Fuel is injected into the passage between the flanges 49 by means of an injector 53 fed with liquid fuel by a fuel supply pipe 54, and fuel is injected into the combustion space of the flame tube at a position just downstream of the annular members 46, 47 by means of an injector 55 having an upstream delivering fuel orifice 56 and a downstream delivering fuel orifice 57.

The fuel injector 53, the air passage between the flanges 49 and the annular member 51, 52 together afford first air and fuel injection means and the air/ fuel mixture entering the upstream region 58 of the combustion space from the first air and fuel injection means partakes of a swirling motion as indicated by arrows 59, in which the mixture first travels from the local centre line of the flame tube towards the annular members '46, 47;, then 'travels upstream, then travels towards the local centre line and finally travels downstream. It is arranged that the air and fuel introduced by the first air/fuel injection means are in their stoichiornetric ratio. a

The holes 50 in the annular members 46, 47 and the fuel injection orifice 56 together afford second air/fuel injection means which produce in a region 69 of the combustion space which is just downstream of the .region 58, a swirling motion which is counter tothe .swirling motion in the region 58, thatis the gases flow from the holes 50 towards the local centre line'of the flame tube, then in the upstream direction, then away from the local centre line towards the annular members 46, 47 and then in the downstream direction. The fuel from the fuel orifice 57 mixes with the combustion products from the combustion zones 58, 60 and is burnt with the excess air therein and with air entering the combustion space through the apertures 44, which also mixes with the combustion gases to cool them.

Referring now to FIGURE 3, there is shown an arrangement which is similar to that shown in FIGURE 1 and similar parts in these FIGURES are given the same reference numerals. However, instead of the spider member 2 4, 25 and fuel injectors 26, 28, an annular trough member 62 is provided to encircle the tube 2-1 adjacent its waist, the annular trough member 62 being concave on its downstream side and a single fuel injector 63 is provided for supplying fuel to both combustion regions. The injector 63 has a peripheral ring of fuel orifices 64 which inject fuel into the air which is flowing into the cap 22, prior to itsentry into the upstream combustion space 65 through the holes 23 in the cap member and the injector 63 delivers fuel from its end 66 through an aperture in the cap member into the combustion region 67.

As in the construction of FIGURE 1 the combustion mixtures in the regions 65 and 66 have counter swirls as indicated by'the arrows 33 and 35.

Referring now to FIGURES 4 and 5, there is illustrated a'further form of combustion equipment which comprises an air casing having a difluser section 76] and a main section 71, and a flame tube disposed within the air casing in spaced relation thereto, the flame tube being formed in a number of sections including an inlet section 72 and a section 73 having large air inlets 74 formed therein.

A tubular member 75 is fitted within the inlet section 72 of the flame tube, the tubular member being domed atits upstream end 75a and having an outwardflange 75b at its downstream end, the flange 75b engaging the wall of the inlet section. The tubular member 75 has a ring of air inlet slots 89 in it adjacent the flange 75b. The domed end 75a of the tubular member 75 has a central inlet 76 facing an inlet 77 at the upstream end of the flame tube section 72, and a tube 78 having a waisted portion extends downstream from'the inlet 76 into the interior of the flame tube. The tube 78 is provided at its downstream end with a frusto-conical skirted cap 79 having a series of slots 80 in its conical surface.

A hollow spider member 81 is fitted in the tube 78 adjacent its upstream end, the boss of the spider member having an inlet 82 facing the inlet 77, and the arms 81a of the spider member extend outwardly and pass through the wall of the tube upstream of its waisted portion to project into the interior of the flame tube just downstream of an annular trough member 83 which has its concave surface facing downstream. The arms 81a have outlets 84 at their outer ends, which outlets are in the form of tangentially-facing slots. Alternatively, the arms may have each a single tangentially-facing slot, the slots facing in the same direction to cause a swirl about the axis of the flame tube.

Fuel is fed to the combustion equipment through a first pipe 85 leading to a nozzle 86 spraying into the spider member and through a pipe 87 leading to a second spray nozzle 88 which is mounted on the spider member stream region 90 of the combustion space is picked up by air from the slots 80 and is caused to swirl in the region 90 in the direction of arrows 91.

The second" air and fuel injection means is afforded by the nozzle 88 and the slots 89. The air from slots 89 swirls as indicated by arrows 93 in the region 92 of the combustion space in a direction contrary to the swirl in the region 90. The fuel from the nozzle 88 passes through the slots and enters the region 92 substantially tangential to the swirling mass of air from the slots 89 and in its passage through the slots 80 entrains a minor proportion of the air flowing through these slots.

In each construction an igniter device 95 is provided in the upstream region 32, 58, 90.

In each of the constructions above described it is found that by arranging combustion to take place in separate and adjacent regions in which counter swirls are produced, the combustion efliciency of the apparatus is improved.

I claim:

1. Gas turbine engine combustion equipment comprising an air casing structure, a flame tube structure housed within the air casing structure, said flame tube structure having walls spaced from the air casing structure to provide an air receiving space externally of the flame tube structure and to provide a combustion space internally of the flame tube structure, which combustion space has an upstream end and a downstream end, said flame tube walls including a tubular upstream Wall portion having an air inlet at its upstream end and a tubular member with a domed end facing the air inlet, said tubular member being supported coaxially within the upstream wall portion in spaced relation thereto and encircling a first and upstream region of the combustion space and a second region of the combustion space immediately downstream of the first region, first air inlet means having outlets therefrom into the combustion space at its upstream end, said air outlets directing a first air flow transversely to the centre line of the flame tube structure into the first and upstream region of the combustion space thereby to produce in said upstream region a first air mass having a swirl in a first direction of rotation, said first air inlet means comprising a tube extending from the domed end coaxially within the tubular member, said tube having an open inlet end facing the air inlet of said upstream wall portion, a cap on the opposite end of the tube, said cap being provided with laterally facing outlet holes through which air is directed transversely to the centre line of the flame tube into said first region of the combustion space, and said first air inlet means also comprising a hollow spider member having an upstream facing air inlet thereto and a series of radiating arms having outlets into said first region of the combustion space, first fuel injection means delivering liquid fuel into said hollow spider member to be conveyed with air flowing through the spider member and the arms thereof into said first region of the combustion space to produce a substantially stoichiometric fuel/ air mixture, a second air inlet means delivering air into the second region of said combustion space which is immediately downstream of said first region, said second air inlet means comprising outlet holes in said tubular member at a position downstream of said cap which outlet holes face the centre line of the flame tube and direct air transversely of the centre line of the flame tube structure to produce in said second region a second mass of air swirling in a direction opposite to the first air mass, and second fuel injection means injecting fuel into the second air mass.

2. Gas-turbine engine combustion equipment according to claim 1, wherein the second fuel injection means extends within said combustion space and sprays fuel upstream into said second region of the combustion space.

3. Gas-turbine engine combustion equipment according to claim 1, wherein said second fuel injection means comprises a fuel injector within said tube spraying fuel through said outlet holes in the cap into said second region of the combustion space.

4. Gas turbine engine combustion equipment comprlsing an air casing structure, a flame tube structure housed within the air casing structure, said flame tube structure having walls spaced from the air casing structure to provide an air receiving space externally of the flame tube structure and to provide a combustion space internally of the flame tube structure, which combustion space has an upstream end and a downstream end, said flame tube walls including a tubular upstream wall portion having an air inlet at its upstream end and a tubular member with a domed end facing the air inlet, said tubular member being supported coaxially within the upstream wall portion in spaced relation thereto and encircling a first and upstream region of the combustion space and a second region of the combustion space immediately downstream of the first region, first air inlet means having outlets therefrom into the combustion space at its upstream end, said air outlets directing a first air flow transversely to the centre line of the flame tube structure into the first and upstream region of the combustion space thereby to produce in said upstream region a first air mass having a swirl in a first direction of rotation, said first air inlet means comprising a tube extending from the domed end coaxially within the tubular member, said tube having an open inlet end facing the air inlet of said upstream wall portion, a cap on the opposite end of the tube, said cap being provided with laterally facing outlet holes through which air is directed transversely to the centre line of the flame tube into said first region of the combustion space, first fuel injection means comprising an injector spraying fuel into air flowing in said tube and entering said combustion space through said laterally-facing outlet holes thereby to supply fuel to said first region of the combustion space to produce a substantially stoichiometric fuel/ air mixture, second air inlet means delivering air into the second region of said combustion space which is immediately downstream of said first region, said second air inlet means comprising outlet holes in said tubular member at a position downstream of the cap which outlet holes face the centre line of the flame tube and direct air transversely of the centre line of the flame tube structure to produce in said second region a second mass of air swirling in a direction opposite to the first air mass, and a second fuel injection means injecting fuel into the second air mass, said second fuel injection means comprising a fuel injection nozzle within the tube spraying fuel through a hole in the cap into said second air mass.

5. Gas turbine engine combustion equipment comprising an air casing structure, a flame tube structure housed within the air casing structure, said flame tube structure having walls spaced from the air casing structure to provide an air receiving space externally of the flame tube structure and to provide a combustion space internally of the flame tube structure, which combustion space has an upstream end and a downstream end, first air inlet means having outlets therefrom into the combustion space at its upstream end, said air outlets directing a first air flow transversely to the centre line of the flame tube structure into a first and upstream region of the combustion space thereby to produce in said upstream region a first air mass having a swirl in a first direction of rotation, first fuel injection means delivering fuel to mix with the air of said upstream region to produce a substantially stoichiometric fuel/ air mixture, second air inlet means delivering air into a second region of said combustion space which is immediately downstream of sad first region, said second air inlet means directing air transversely of the centre line of the flame tube structure to produce in said second region a second mass of air swirling in a direction opposite to the first air mass, and a second fuel injection means injecting fuel into the second air mass, said flame tube structure having fitted within it at its up stream end a tubular member having a domed upstream end and defining with the flame tube structure air passages extending lengthwise of the flame tube, which passages at their downstream ends have air outlets facing transversely of the centre line of the flame tube into the second region 7 of the combustion space and forming in part said second air inlet means, said tubular member having in its domed end an air' inlet, a tube mounted centrally of said tubular member and extending downstream from said inlet, said tube having at its downstream end laterally-facing air outlets into said first region of the combustion space, and a hollow spider member accommodated within said tube adjacent its upstream end and having a hollow bos and hollow radiating arms extending through the wall of the tube to open into the combustion space adjacent said first region, said spider member forming in part said first air inlet means, said first fuel injection means delivering fuel into said spider member to be carried by air flowing therethrough into said first region of the combustion space.

6. Gas-turbine engine combustion equipment according to claim 5, wherein said second fuel injection means comprises a fuel injector within the combustion space and downstream of said second region, said fuel injector being arranged to deliver fuel in the upstream direction into said second region.

7. Gas-turbine engine combustion equipment according to claim 6, wher in said fuel injector is also arranged to spray fuel into the combustion space in a direction downstream from said second region.

8. Gas-turbine engine combustion equipment according to claim 5, wherein the second fuel injection means comprises a fuel injector supported by said spider and extending within said tube and arranged to spray fuel through the air outlets from the tube at an angle such that the fuel spray flows into the second region substantially tangentially of the swirling gases therein.

9. Gas turbine engine combustion equipment comprising an air casing structure, a flame tube structure housed within the air casing structure, said flame tube structure having walls spaced from the air casing structure to provide an air receiving space externally of the fiame tube structure and to provide a combustion space internally of the flame tube structure, which co ibustion space has an upstream end and a downstream end, first air inlet means having outlets therefrom into the combustion space at its upstream end, said air outlets directing a first air 'fiow transversely to the centre line of the flame tube structure into a first and upstream region of the combustion space thereby to produce in said upstream region a first air mass having a swirl in a first direction of rotation, first fuel injection means delivering fuel to mix with the air of said upstream region to produce a substantially stoichiometric fuel/air mixture, second air inlet means delivering air into a second region of said combustion space which is immediately downstream of said first region, said second air inlet means directing air transversely of the centre line of the flame tube structure to produce in said second region a second mass of air swirling in a direction opposite to the first air mass, and a second fuel injection means injecting fuel into the second air mass, the flame tube structure having fitted within it at its upstream end a tubular member having a domed upstream end and defining with the flame tube structure air passages extending lengthwise of the flame tube which passages at their downstream ends have air outlets delivering into the second region of the combustion space and forming in part said second air inlet means said tubular member having in its domed end an air inlet, a tube mounted centrally of said tubular member and extending downstream from said inlet, said tube having at its downstream end air outlets into said first region of the combustion space, said outlets, from the tube forming the first air inlet means, a fuel injector located within said tube and having first fuel orifices forming said first fuel injection means and delivering fuel through said outlets to the first region of the combustion space and a further 1 orifice forming said second fuel injection means and directing fuel through an aperture in the downstream end of the tube into said second region of the combustion space.

References Cited in the file of this patent UNITED STATES PATENTS 2,143,259 Clarkson Jan. 10, 1939 2,529,506 Lloyd et a1 Nov. 14, 1950 2,545,495 Sforzini Mar. 20, 1951 2,546,432 Darling Mar. 27, 1951 2,560,207 Berggren et a1. July 10, 1951 2,601,000 Nerad June 17, 1952 2,635,426 Meschino n- Apr. 21, 1953 2,638,745 Nathan May 19, 1953 2,667,033 Ashwood Ian. 26, 1954 2,679,137 Probert May 25, 1954 2,704,435 Allen Mar. 22, 1955 2,930,192 Johnson Mar. 29, 1960 FOREIGN PATENTS 505,778 Italy Dec. 18, 1954 

